With the development of mobile communication systems, several wireless communication standards (i.e., wireless communication schemes) have been developed. Some exemplary wireless communication schemes include global system for mobile communications (GSM), personal digital cellular (PDC), and cdmaOne (IS-95), which are second generation (2G) wireless communication schemes. Other exemplary wireless communication schemes include time division-synchronous code division multiple access (TD-SCDMA), wideband CDMA (W-CDMA or WCDMA), and CDMA2000, which are third generation (3G) wireless communication schemes. Other exemplary wireless communication schemes include general packet radio service (GPRS), and Enhanced Data Rates for GSM Evolution (EDGE), which are from-2G-to-3G wireless communication schemes. Wireless local area network (WLAN) is another popular wireless communication scheme.
Some conventional wireless communication devices are designed to operate with multiple wireless communication schemes. As an example, a traditional W-CDMA/GSM terminal is used to provide 2G/3G network coverage and/or load balancing. As both the GSM and W-CDMA operabilities belong to one operator (or based on the roaming agreement between operators), the conventional W-CDMA/GSM terminal has only one subscriber identity module (SIM) card slot for one subscription, and only one phone number is used. Consequently, a conventional W-CDMA/GSM terminal does not transmit and receive in both modes at the same time.
As an alternative, where dual SIM card slots are implemented for two subscriptions (i.e., one SIM card slot is for a GSM operator, and the other SIM card slot is for a different W-CDMA operator), then the dual standby terminal operates with two phone numbers online at the same time. However, the simultaneous transmitting of one mode and the receiving of another mode would lead to detrimental radio frequency (RF) interference. Moreover, implementing a dual standby terminal with two chipsets (i.e., one chipset for each mode) would increase the cost and size of the dual standby terminal and decrease performance.
Designed to operate in a single mode at a time, the conventional terminal, including its processing power, memories, buffers, and timing controls, is tailored to a single mode running requirement. If two modes attempt to run at the same time in a dual standby manner, the conventional terminal architecture would not support such operability.
Additionally, it should be noted that inter-system measurements are not active all the time in a traditional single standby terminal. FIG. 1 depicts an exemplary paging scheme 10 for a conventional single standby wireless terminal. In particular, the conventional terminal receives paging information 12 for the active mode on a regular basis, but only receives the inactive mode's network signal 14 when the inter-system measurement is executed. The inter-system measurements are triggered by a vendor-specific algorithm implemented at a base station such as a radio network controller (RNC) of a W-CDMA network. Thus, if the dual standby terminal is simply implemented by adding another SIM card slot on the conventional terminal architecture, it will potentially miss calls or incoming communications that are attempted on the inactive mode while the terminal is operating in the active mode.